Tag Archives: Hansen

I have written a number of times about the “global warming accelerating” meme. The evidence is nearly irrefutable that over the last 10 years, for whatever reason, the pace of global warming has decelerated (click below to enlarge)

This is simply a fact, though of course it does not necessarily “prove” that the theory of catastrophic anthropogenic global warming is incorrect. Current results continue to be fairly consistent with my personal theory, that man-made CO2 may add 0.5-1C to global temperatures over the next century (below alarmist estimates), but that this warming may be swamped at times by natural climactic fluctuations that alarmists tend to under-estimate.

Anyway, in this context, I keep seeing stuff like this headline in the WaPo

Scientists: Pace of Climate change Exceeds Estimates

This headline seems to clearly imply that the measured pace of actual climate change is exceeding previous predictions and forecasts. This seems odd since we know that temperatures have flattened recently. Well, here is the actual text:

The pace of global warming is likely to be much faster than recent predictions, because industrial greenhouse gas emissions have increased more quickly than expected and higher temperatures are triggering self-reinforcing feedback mechanisms in global ecosystems, scientists said Saturday.

“We are basically looking now at a future climate that’s beyond anything we’ve considered seriously in climate model simulations,” Christopher Field, founding director of the Carnegie Institution’s Department of Global Ecology at Stanford University, said at the annual meeting of the American Association for the Advancement of Science.

So in fact, based on the first two paragraphs, in true major media tradition, the headline is a total lie. In fact, the correct headline is:

“Scientists Have Raised Their Forecasts for Future Warming”

Right? I mean, this is all the story is saying, is that based on increased CO2 production, climate scientists think their forecasts of warming should be raised. This is not surprising, because their models assume a direct positive relationship between CO2 and temperature.

The other half of the statement, that “higher temperatures are triggering self-reinforcing feedback mechanisms in global ecosystems” is a gross exaggeration of the state of scientific knowledge. In fact, there is very little good understanding of climate feedback as a whole. While we may understand individual pieces – ie this particular piece is a positive feedback – we have no clue as to how the whole thing adds up. (see my video here for more discussion of feedback)

In fact, I have always argued that the climate models’ assumptions of strong positive feedback (they assume really, really high levels) is totally unrealistic for a long-term stable system. In fact, if we are really seeing runaway feedbacks triggered after the less than one degree of warming we have had over the last century, it boggles the mind how the Earth has staggered through the last 5 billion years without a climate runaway.

All this article is saying is “we are raising our feedback assumptions higher than even the ridiculously high assumptions we were already using.” There is absolutely no new confirmatory evidence here.

But here is the problem: The creators of these models are now saying that actual CO2 production, which is the key input to their model, is far exceeding their predictions. So, presumably, if they re-ran their predictions using actual CO2 data, they would get even higher temperature forecasts. Further, they are saying that the feedback multiplier in their models should be higher as well. But the forecasts of their models are already high vs. observations — this will even cause them to diverge further from actual measurements.

So here is the real disconnect of the model: If you tell me that modelers underestimated the key input (CO2) in their models, and have so far overestimated the key output (Temperature), I would have said the conclusion to this article is that climate sensitivity must be lower than what was embedded in the models. But they are saying exactly the opposite. How is this possible?

Postscript: I hope readers understand this, but it is worth saying because clearly reporters do not understand this: There is no way that climate change from CO2 can be accelerating if global warming is not accelerating. There is no mechanism I have ever heard by which CO2 can change the climate without the intermediate step of raising temperatures. Co2–>temperature increase–>changes in the climate.

Update: Chart originally said 1998 forecast. Has been corrected to 1988.

Update#2: I am really tired of having to re-explain the choice of using Hansen’s “A” forecast, but I will do it again. Hansen had forecasts A, B, C, with A being based on more CO2 than B, and B with more CO2 than C. At the time, Hansen said he thought the A case was extreme. This is then used by his apologists to say that I am somehow corrupting Hansen’s intent or taking him out of context by using the A case, because Hansen himself at the time said the A case was probably high.

But the only difference between A, B, and C were not the model assumptions of climate sensitivity or any other variable — they only differed in the amount of Co2 growth and the number of volcano eruptions (which have a cooling effect via aerosols). We can go back and decide for ourselves which case turned out to be the most or least conservative. As it turns out, all three cases UNDERESTIMATED the amount of CO2 man produced in the last 20 years. So, we should not really use any of these lines as representative, but Scenario A is by far the closest. The other two are way, way below our actual CO2 history.

The people arguing to use, say, the C scenario for comparison are being disingenuous. The C scenario, while closer to reality in its temperature forecast, was based on an assumption of a freeze in Co2 production levels, something that obviously did not occur.

Over at the Blackboard, Lucia has a post with a growing set of comments about anthropogenic warming and the tropical, mid-tropospheric hotspot. Unlike many who are commenting on the topic, I have actually read most of the IPCC AR4 (painful as that was), and came to the same conclusion as Lucia: that the IPCC said the climate models predicted a hot spot in the mid-troposphere, and that this hot spot was a unique fingerprint of global warming (“fingerprint” being a particularly popular word among climate scientists). Quoting Lucia:

I have circled the plates illustrating the results for well mixed GHG’s and those for all sources of warming combined. As you see, according to the AR4– a consensus document written for the UN’s IPCC and published in 2007 — models predict the effect of GHG’s as distinctly different from that of solar or volcanic forcings. In particular: The tropical tropospheric hotspots appears in the plate discussing heating by GHG’s and does not appear when the warming results from other causes.

OK, pretty straight-forward. The problem is that this hot spot has not really appeared. In fact, the pattern of warming by altitude and latitude over the last thirty years looks nothing like the circled prediction graphs. Steve McIntyre does some processing of RSS satellite data and produces this chart of actual temperature anomalies for the last 30 years by attitude and altitude (Altitude is measured in these graphs by atmospheric pressure, where 1000 millibars is the surface and 100 millibars is about 10 miles up.

The scientists at RealClimate (lead defenders of the climate orthodoxy) are not unaware that the hot spot is not appearing. They responded about a year ago that 1) The hot spot is not an anthropogentic-specific fingerprint at all, but will result from all new forcings

the pattern really has nothing to do with greenhouse gas changes, but is a more fundamental response to warming (however caused). Indeed, there is a clear physical reason why this is the case – the increase in water vapour as surface air temperature rises causes a change in the moist-adiabatic lapse rate (the decrease of temperature with height) such that the surface to mid-tropospheric gradient decreases with increasing temperature (i.e. it warms faster aloft). This is something seen in many observations and over many timescales, and is not something unique to climate models.

and they argued 2) that we have not had enough time for the hot spot to appear and they argued 3) all that satellite data really has a lot of error in it anyway.

Are the Real Climate guys right on this? I don’t know. That’s what they suck up all my tax money for, to figure this stuff out.

But here is what makes me crazy: It is quite normal in science for scientists to have a theory, make a prediction based on this theory, and then go back and tweak the theory when data from real physical processes does not match the predictions. There is certainly no shame in being wrong. The whole history of science is about lurching from failed hypothesis to the next, hopefully improving understanding with each iteration.

But the weird thing about climate science is the sort of Soviet-era need to rewrite history. Commenters on both Lucia’s site and at Climate Audit argue that the IPCC never said the hot spot was a unique fingerprint. The fingerprint has become an un-person.

Why would folks want to do this? After all, science is all about hypothesis – experimentation – new hypothesis. Well, most science. The problem is that climate science has been declared to be 1) A Consensus and 2) Settled. But settled consensus can’t, by definition, have disagreements and falsified forecasts. So history has to be rewritten to protect the infallibility of the Popethe Presidium the climate consensus. It’s a weird way to conduct science, but a logical outcome when phrases like “the science is settled” and “consensus” are used as clubs to silence criticism.